FIG. 1 shows a conventional network connected by routers. Routers use logical and physical addressing to connect two and more logically separate networks. They accomplish connection by organizing the large network into logical network segments which are also called subnetworks or subnets. Each of this subnetworks is given a logical address, allowing the networks to be separate but still access each other and to exchange data when necessary. Data is grouped into packets or blocks of data. Each packet, in addition to having a physical device address, has a logical network address. The network address allows the routers to more accurately and efficiently calculate the optimal path to a workstation or computer. Rooting is provided by a hardware device that operates at the network layer. A router may be an internal device or a stand alone unit that has its own power supply.
Since a router operates at the network layer it is dependent on the protocol being used. The protocol determines the address format in the packets. Thus, an IP (Internet Protocol) router is not able to handle the packets for instance with addresses in X.25 format. A router can work with different data link layer protocols. Multiprotocol routers can handle several data link layer protocols. As a result, a router can be used as a packet filter based on network protocols as well as addresses. Because it is independent of data link layer protocols a router can connect networks using different architectures, for example Ethernet to Token Ring or Ethernet to FDDI.
Several levels of routers can be defined. For example, a particular city might have building-level routers. Each router knows how to find a path from a node in its building to a node in another building. Basically the router has the task of getting a data packet to the router for the destination building. When for instant the building level router receives a packet, the router checks whether it is intended for the building. If so, the router passes it through to the floor for which the packet is intended. If not, the router determines a path to the destination building.
FIG. 2 shows a block diagram of a conventional router according to the state of the art. The router as shown in FIG. 2 is a router for the state of the art internet protocol version 4 (IPv4). The router comprises a routing core which is a hardware device connected to other routers or servers and to terminals or personal computers. The router comprises a memory for storing a routing table and a search engine which searches the routing table for a matching data entry when a new data packet is received by the routing core. A routing table of the router is actualized permanently using routing protocols such as BGP (Border Gateway Protocol) or OSPF (Open Shortest Path First). With the routing protocols the router determines signal paths for packets by communicating with neighboring routers at their level. Routers can request and obtain information about data paths from the neighbor to still other routers. Since routers operate at the network layer they are sensitive to the protocol being used. Thus, a router that can handle IP packets can not handle IPX packets without addition of special capabilities. Single protocol routers were the rule for many years. In the natural course of technological evolution routers expand the capability with respect to the network level protocol supported. High end routers can process packets from more than one type of protocol.
The Ipv4 router according to the state of the art as shown in FIG. 2 has the drawback that the memory for the routing table needs a lot of storing capacity since the routing table to be stored has a lot of data entries. In an Ipv4 network the addition of a new router into the network makes it sometimes necessary to change the routing tables worldwide. The main reason for this is that IPv4 networks are not formed hierarchically. The current internet is based on the internet protocol version 4 (IPv4). The twenty years old IPv4 protocol makes it necessary for routers to store a very huge routing table, typically 100 K to 250 K entries.
The internet protocol version 6 (IPv6) is expected to be the key enabling technology for the next generation internet which allows communication in computing anywhere, at any time in a secure manner. The new features of IPv6 include a large address space with 128 instead of 32 bits source and destination addresses and an efficient hierarchical addressing scheme. IPv6 data packets comprise a simplified header format.